Dave, those ‘referals’ from Silicon Investor may not be true visitors. I get lots of sites in my referal logs that are basically spam. Most are porn sites, others are stocks or Nigerian scam type sites.

They are trying to get you to go to their site after noticing their URL in your logs. Some of these also try and get themselves listed on those ‘Last Five Referring Sites’ sidebars of some webpages or weblogs.